Regulating apparatus.



H. BULLOCK. REGULATING APPARATUS. I APPLIOATION FILED MAY 4, 1912.

a sums-sum 1.-

Patent ed Sept. 9, 1913.

' H; BULLOCK. REGULATING APPARATUS. APPLICATION FILED MAY 4, 1912,

1,73pg5, I Patented Sept. 9, 1913.

5 SHEETS-SHEET 2.

H. BULLOCK. REGULATING APPARATUS. APPLICATION FILED MAY4, 1912.

'1 73,025, Patented Sept. 9, 1913. V

5 SHEETS-SHEET 3.

' IIIIIII" 'I/III H. BULLOCK. REGULAT'ING APPARATUS.

APPLICATION FILED MAY 4, 1912.

1,073,025. v Patented Sept. 9, 1913.

5 SHEETS-*SHEBT 4.

H. BULL-06K. REGULATING APPARATUS.

APPLICATION FILED MAY 4, 1912.

9/1913. 5 SHEETS-SHEET 5.

Patents hllll ram: oFFICEQ i-mnnnar BULLOCK, or theorem ENGLAND.

nneomrmo humerus.

Speeifieation of Letters Patent.

Patented Sept. 9, 1913.

Application filed ma 4, 1912. Serial No. 095,109.

To all w from 2'15 may concern:

Be it known that I, HERBERT BULLOCK, a

subject of the'King of Great Britain, residing at 13 Northdale road, Frizinghall, Bradford, Yorkshire, England, have invented certain new and useful Improvements in Regulating; Apparatus; and I do herebydeclare the following to be a full, clear, and exact description of' the invention, such as will enable others skilled in the art to which it appertains to make and use thesame;

This invention reiatesto improvements in in the boilers, the speed at which an auto-' matic Stoker works according to the pressure of steam in the boiler or according to the temperature in the part to be heated by the furnace, the speed at which carbons in arc lamps are fed together according to the resistance between the carbons, the rate at which blowers or the like are operated according to the pressure produced by the said blowers and analogous purposes.

In the accompanying drawings the inven-,

tion is illustrated byway of example as appliedto the rotation in one direction or other of a spindle such as can'be connected nip to the dampers in a balanced draft system for boiler furnaces and to the rotation of a spindle in one direction such as may be connected up to the feed for an automatic stoker for boiler furnaccs,.tl1e relay device itself being controlled by the pressure of steam in the boiler through a Bourdon tube. in this case the spindle may be termed the mechanism which is operated and the Bozo-don tube the controlling; device 'which is subjected to and automatically'adjustod by alterations i'roin the normal or de sired ('(llHl l'lUll ol' the part or mechanism oi which it is desired to keep the temperature or pressure or other condition zis the ('nsc may be constanl or approximately so. i uthe purposes oi description the Bour- (lon flflfl't or llH. WgllHilitEllt will be shortly (emu-d 1" the controlling device.

.l he (Il) |0(;i oi the invention are :to provide a relay mechanism which shall be'very sensitive to slight variations in the "condition to be controlled. Further toarrange so that the amount of movemen't imparted to the mechanism which is operated may automatically vary or. be varied by hand adjustment relativetothe amount of movement of the controlling device. .Further to arrange that a slight variation in the con dition to be controlled or of the controlling device mayonly result in a. relatively small movement (or if desired relatively large movement) of the mechanism which is operated while a further variation as above may result in a relatively large (or if desired relatively small)'-- movement of the mechanism which is operated. Further to arrange for the mechanism to 'be operated to take up definite fixed positions corresponding to the respective pressures 'within 1 the range of the regulator. Further to arrange so that the relative speed of movementimparted to the mechanism which is v operated maybe relatively larger for the variation in the condition to 'befcontrolled on one'side of the normal condition than the amount of movement imparted A0 the said mechanism for a correspondin amount of variation on the other side of t 1e normal or desired condition.

In the embodiment of the invention shown in the aco ompanying drawings :-Figure 1 is an end elevation partly i section of an apparatus adapted for control ing the dampers in a boiler furnace. Fig. 2 is a vertical axial cross section of Fig. 1. Fig. 3 is an end elevation partially in section of the device as modified for cntrolling the movement in one direction of the part to be operated such as the feed of a mechanical stoker. Fig. 4 is an elevation of the device showmg the means for automatically adjusting the relative rates of movement of the controlling device and the mechanism which is to be o erated. Fig. 5 is a plan view of Fig. 4. igs. 6 and 7 are small detail views hereinafter referred to. Fig. 8 is a diagrammatic view of different arrangement of shield hereinafter referred to. Fig. 0 shows a modified foim of pallet hereinafter referred to. Fig. 10 is a sectional vi'ew taken on the line 10 -10 of Fig. 2; and Fig. ll is a detail view, in elevation, of the transmission gearing between the device and the part to be controlled.

In these drawings-1 is a Bourdon tube,

. bearings 20.

'acting as the controlling device, suitably connected by the pipe 2 to a source of pressure, in this case supposed to be a boiler, the dampers in the tines of which are controlled by the relay mechanism. The relay mechanism itself consists of the arm which is provided with reversed pawls or engaging means 4 and 5 which rock over a ratchet wheel with reversed sets of teeth 6 and 7. This ratchet wheel is firmly mounted on a central spindle S carrying a worm 9 which controls by means of the toothed sector 10 a rod or spindle 11, which as before stated is in this example the mechanism which is operated. The ratchet wheel is provided with a boss 6 and loosely mounted thereby on the spindle 8. ,he reversed set of teeth 6 is secured to the main part of the ratchet wheel carrying the set of teeth 7 by suitable screws or bolts 7. The pawl arm 3 is mountcd so as to swing freely about the boss (5. The lower end of the pawl arm 3 provided with a slot -13 in which is located a crank pin 12' mounted on the side of the worm wheel 1 which latter is mounted on. a stud 1d and continuously rotated from the worm 15 mounted on a continuously rotating shaft 15. The pawls 4; and 5 are mounted on a stud 16 which is rigidly secured to and projects from the rocking pawl arm 3. Between the engaging means or pawls and the reversed ratchet wheel is arranged a shield 17 which is of sullicient length to cover in its central. position those parts of the ratchet wheel under both pawls so as to hold these latter normally out of engagement with the corresponding sets of teeth. This shield 17 is formed integral with or supported by a radial arm 18 rigidly mounted on the spindle 19 carried by needle point Also mounted on the spindle 19 so as to be capable of turning freely about the same are two upstanding fingers 21 connected together by a spring 22 so that their upper and outer extremities lie against or partially embrace the stud 35 on .the radial arm 18 carrying the shield 17.

These upstanding fingers 21 also partially embrace or normally rest against an extension 16: of the stud 16 upon which the pawls 1 and 5 are mounted. The shaft 19 has secured to its underside the chamfered disk 23 which is'located just above a double "pallet 2-1 mounted upon a stud 25 hearing with needle point bearings 36 in suitable supports 25 forming anescapement device. The Bourdon gage 1 is connected by a link 26to a lever 27. This lever 27 at its free end slides in the end of a spring 28 which forms a fulcrum for it. The other end of thelever 27 carries an upstanding rod 29 the outer end of which under normal conditions just touches the underside: of the double pallet 2 1. This pallet 13 also connected to the link 26 by means Jf a tension 81 carric. a cam or eccentric 39 which supports one end of the spring 28 the eccentric or cam 39 being capable of being turned from the thumb nut 32 to raise and lower the spring 28. y p

In Figs. 1, 5 and 6 the spindle 11 is provided at the outside with a double bracket 52 carrying a screw threaded bolt 53 upon which is mounted a nut 15 one side of which is pivoted to a link 16. This link is also connected to a bell crank lever 17 pivoted to the outer case of the apparatus at 48 and connected by its other end to a loosely mounted crank 49 on the spindle 31. The thumb nut 32 carries two bolts 50 the heads of which engage slightly over the crank 1!) shown in Figs. 5 and (3, the said bolts being capable of being tightened so as to hold the crank 1-9 against the thumb nut by suitable nuts 51.

The action of the device thus far described is as follows: The shaft 15 is continually rotated and continuously rotates the worm whecllZ-l through the worm 15 which worm wheel by means of the crank pin 12 oscillates the pawl arm 3 with its projecting stud 10 and the pawls or engaging means 1- and 5. The oscillations of the extension 16' of the stud 16 cause the fingers 21 also to oscillate. These fingers 21 in turn, owing to the stud 35, cause the shield 17 to oscillate with the pawls and so oscillate the shaft 19 and the chamfercd disk 23. This is the action under normal conditions. On however the pressure in the Bourdon gage rising the same'will open somewhat and in opening lift the lever 27 and cause the upstanding rod.2.) to tilt the pallet 24: against the action of the spring 30. This tilting of the pallet will cause the left hand arm of the same to rise into the path of the oscillating disk,23 and so prevent it from being moved to the left hand and will so prevent the shield from being moved to the right. This however will not prevent the pawls from continuing to oscillate so that the pawl 5 will in its oscillation drop oil the shield 17 and come into contact with the ratchet wheel and the set of teeth 7 and so will rotate the same clockwise, which will rotate the spindle. 8 in the same direction and so turn the shaft 11, that is to say, the mechanism which is to be operated. This mechanism to be operated or shaft 11 is, in the application of the invention shown,'supposed to be connected to suitable means to reduce the pressure in the boiler for instance by closin the dampers in the lines. As the pressure Tails the pallet 24 will resume its normal position so'tha-t the disk 23 can again rock and permit the shield to be oscillated to both sides as before.

ovelace Should the pressure drop to wanna an cXlcnt' the reverse action to the above will take place that is to say,.the pawl {will-beable ti'fccme. into contact with the set of ;=,-eth 6 and turn the shaft 11 or mechanism to be operated in the reverse direction. It will be noted that the effect of holding the disk 23 against oscillation in one direction is to hold the radial ar1n-18 with. itsstud 3.5 also against oscillation. As the upstanding fingers 21 are only connected together by the spring 22 it will he obviously possible for the stud to hold one against oscillation in one direction while the extension 16 on the stud 16 carries the other finger' with it without oscillating the shield in 3%) be "turned so as to lower the rod 29 the amount of variation in pressure needed to bring the relay into action will be increased. In the modification shown in- Figs. 5, 6 and 7 the turning of the spindle 11 itself automatically turns the cam 39 so that the cam may be used to neutralize for a short period or to increase or again to decrease the transmission of motion from the Bourdon' gage to the pallet in the same manner as if the hand out 32 in Fig. 2 were turned by hand. If the cam be of the shape shown in Fig. 7 the turning of the camfrom the spindle 11 will tend to diminish the amount of motion imparted by the Bourdon" gage to the pallet in the early travel. of the spindle 11 from its normal psition. The further turning of 1his cam, however, will bring a concentric 'iortion of": the same under the spring-so that any further turning beyond this point will not in any way affect the speed of transmission of the motion from the Bourdon gage to the pallet. Supposing for a moment that the device is being used for controlling On this further variation the operation will be repeated the damper being caused to take -u'p definite positions fbr the different pressures, being moved step by step until the variation iu-pressure becomes great enough to bring the concentric portion of the cam under the spring after which its further turning will have no effect on the pallet clro when the reverse of the action above described will take place.

Obviously-a loweringof thepressure from the normal or desired pressure will cause the damper to move in the opposite direction and the cam will beturned in a counter clockwise direction. In this way the damper will have definite fixed positions correspondmg to the respective pressures within the range of the regulator.

If the cam 39' has a uniform eccentricity it-is obvious that the amplitude of movement -which will then be solelyaifected by the Bourdon gag'e until thepressure begins toof the damper will be uniform for a given variation in pressure throughout the entire range of pressure through which the regulator works; that is from the pressure at which the damper is in its position of minimum opening to the pressure at which the damper is in its position of maximum opening. It' is also obvious that by ;hanging the shape. of the cam 39-, varying amplitudes of movement of the damper or other mechanism can be obtained for a given variation 'of pressure or other condition-at different points within the range oi the regulator.

. In Fig. ,3 a relay device is shown in which a shaft rotated in one direction only, the relay device not only rotatin the shaft but regulating the speed at whic it is rotated.

In this case instead of the pallet 24 and disk 23 there is arranged a single finger 44 projecting from and rigidly secured to the spindle 19 and a single arm 34 one end of which is stepped and is raised at times into the .path of the oscillating finger 4A the other end being secured to effect this result to the Bourdon gage tube 1 and being operated therefrom e actly in the same manner as described w' reference to Fig. 1. The action of the stepped end of the swinging arm 34 is co-allow the ratchet wheel 7 to be rotated at a smaller speed for small variations from the normal pressure; In the position shown in the drawings it is assumed that there is a stationary by the arm 34, which permits the pawl 5 to forcethe ratchet wheel 7 around a maximum amount for each of its oscillations. On the arm falling a sm'all'amount owing to the variation from the normal decreasing, the finge-r 44 instead of being. held against oscillation will oscillate-the amount of the first step on the arm 34 which will cause the shield 17 to oscillate to the extent large variation so that the shield 17 is held 7 of one tooth on the ratchet wheel 7..and so means of the set screws 12.

This effect will'take place to an increased extent as the arm is lowered and until it is quite out of the path of the linger it when the shield will'rock entirely with the pawl 5 so that no rotation will be imparted to the ratchet wheel 7.

By making the shield in the arrangen'ient shown in Fig. 1 somewhat larger on one side of its center than on the other as shown by dotted lines atl? the number of teeth operated by the respective pawls will be. diliierent so that it will be obvious without further explanation that it will be possible thereby toobtain quick movement o'f the mechanisnrto be operated in one direction and a slow movement in the other. ()ver each set of teeth 6 and 7 of the ratchet wheel there may be arranged a v:l urther permanently adjustable shield so that the total amount of nioven'ient: imparted to the ratchet wheel will be limited to a predetermined amount. this means it is possible to arrange thatin the present case the dampers shall 'not be wholly closed it such a condition be desired or the travel of the lever may be regulated to any desired extent. For this purpose a ring 4E1 Fig. 2 carrying a shield ll and rotatably mounted between the two parts of the'ratchet wheel may be used. This ring l1 may be clamped to the ratchet wheel in any desired position by The shield 4. 1 will naturally have to cover up the ratchet wheel for a distance greater than the length of travel of the respective pawl (except as hereinafter described) so that the latter will. eeaseto act on theratchet wheel when it has turned the latter through the desired angle. In a modification of the arrangement just described with a double pallet and reversed sets of teeth on the ratchet wheel the oscillating shield 17'may be used In conjunction with two fixed shields for each set of teeth adjustably attached to the ratchetwheel by means of tltfring 4:1 as shown diagrammatically in fig. 8 one of whichshields 6 v or 7 in each case covers a shorter arc of the ratchet wheel than the arc the pawl arm swings through and the other 6 or 7? a.

greater arc. In this case the pallet-itself is formed as in Fig. 9 to vary the throw of the pawls according to thevariation in pressure as is thecase with the stepped arm 34 in Fig. 3. 'Owing to the shape of the pallet arms there is obviously no need for teeth to be formed on them. By this arrangement it is possibleto arrange for the dampers, where such are being controlled or the corresponding part, to be controlled or operated I to a limited extentunless the pressure on temperature or other condition varies to .an excessive amount when the dampers could be completely closed. The reason for this 'is that if the number of teeth acted on by the'pawl is limited by ther'shield 17 osciltrolling device.

lating with the pawls to a certain extent,

the shorter fixed shield will prevent the pawl from acting on the ratchet wheel. In

this position the dampers or the like would be nearly closed. If for some reason this amount of closing is not sufficient and. the;

pressure rises still further and the pallet entirely stops the movable shield 17 from. oscillating with the pawls then the pawl can act on the teeth of the ratchet Wheel behind the 7 shorter shield and r so rotate the ratchet wheel until the larger shield is reached.

in the -foregoing description the relay device has only been described for controlling the dampers in. boiler lines and for regulating the speed of operation of a mechanical stoker or the like, The device is, however. as stated above applicable for many other purposes and may be controlled by means of a thermostat or by electric or other means to control the desired condition.

I declare that what I claim is I 1. in a relay apparatus forthe purposes described, a mechanism to be operated, a Controlling device. a ratchet wheel connected to the mechanism to be operated, a pawl device over said ratchetwheel, nieans 'l'or oscillating said pawl device: aboutsaid ratchet wheel, a shield between said pawl device and the ratchet wheel, means for normally oscillating said shield synchronously 4 with said pawl device to hold said )awl de vice out of engagement with sai ratchet wheel; and means connected to said contr0lling device for at certain times arresting the said shield in its oscillation with said pawl device substantially as described.

2. In a relayapparatus for the purposes described, a mechai'iisni to be operated, a controlling device, a ratchet and pawl device connected to. said mechanism to bejoperated, a shield connected to and synchronbusly operable with the pawl devices adapttd to,

normally hold=said pawl devices in ino erative position; and an eecapement device con nected to saidratchet and pawl device and adapted to effect the release of said shield, the escape-merit being controlled by said coniii In a relay apparatus for the purposes described, a mechanism to be operated, a controlling device, a constantly rotated I shaft, an arm oscillated from said constantly rotated shaft, a' toothed wheel connected to said mechanism to be operated, means for 12 engaging with said method wheel mounted on said oscillating arm, a shield. mounted between said toothed wheel and said engaging means and normally synchronously operable with said engaging means, means for normally oscillating s 1d shield with said engaging means, means connected to said controlling device for at times arresting the oscillation of the shield substantiz'illfr' as described. 1 30 4. In a relay apparatus for the purposes described, a mec anism to-bc operated, a controlling device, a ratchet and pawl device connected to said mechanism to be operated, means for oscillating and nor- "mallyholding the engaging means of said ratchet and pawl tglfstive position said holding means nor;-

man oscillating with said engaging means, an escapement device connected I to said holding means said'escapement bedevice.

ing connected to the controllingl t e purposes -5. In a relay apparatus for" I described, a mechanism to be operated, a

- controlllng device.

controlling device, a, ratchet and pawl device connected to said mechanism to be eperated, ashield located between the engaging means and ratchet of said ratchet-and pawl device, means for oscillatiii' the engaging means of said ratchet and pawl device, means 'for normally oscillating said shield with the engaging means of [said ratchet and pawl device,'meai1s for at times arrest-i evioc in aninop;

ment device, operative connections between l said esc'apement device and said means for normallyholding said ratchet and pawl degagin vice inoperative, "said escapement itself being connected to said controlling device.

In a relay apparatus for the purposes described, a mechanism to be operated, a; controllingj'device, a ratchet wheel, con-' stant-ly oscillating means for engaging with said ratchet. wheel, aconstantly osc llated arm, a stud carried by said arm, the said stud carrying said engaging means, a shield located between said enga ing means and said ratchet wheel, a sha t co-axial with said ratchet wheel, an armjon said "ha-ft carrying said shield, means loosely mo nted on said shaft enga g withsaid radial arm andwith said stud o normally oscillate saidshield with said engaging means, means connected to said controlling device for at times arresting the shield in its oscillation With said en g e n 8. In a relay apparatustfor the purposes described, a mechanismgto be operated, a controlling device, a ratchet wheel connected to said mechanism to be operated, means for engaging with said ratchetwheel, meansfor constantly oscillating said engaging means about said ratchetr wheel, a stud car;- rying said engagingmeaiis, a shield located between said ratchet wheel and said engaging means, a shaft coaxial with said ratchet,

wheel an arm rigidly secured to said shaft and carrying said shield, a projection from said e'ng'agii means, loose upstanding fingers mou'nt'e' on Said shaft and extending each up one sideof said radial arm supportmg sa d, shieldand onpne side of the said eittensicn, atension spring between said upstanding fingers and an escapement device, one part mounted on said shaft and another part connected to said controlling device substantially asdescribed. v I 9. Infa relay apparatus for the purposes" descrihcdfa, mechanism to be operated, a coiitrolling, device, a ratchet wheel connected to said controllin device, engaging means for said r'atchet whehmeans for oscillatii said engaging means to and fro over'sar ratchet wheel, a shield located between said engaging poems and said ratchet wheel,

spring means ,betwenfsaid engaging means and said shield for normally oscillating said shield with said engaging means and means connected to sald controllm device for attimes arresting the oscillation of said shield with said on aging device.

10. In are ay'apparatus for the purpose described, a mechanism, to :be operated, u controlling device, a ratchet wheel connected to said mechanism to be operated, engaging means for said ratchet whee l,.means for os cillating said engaging means about said ratchet wheel, holding means for holding said engaging means out of operative'connection with said ratchet wheel,said holding means normally oscillating with said enmeans, a part rigidly connected to said's ield, an angularly adjustable device, means for conveying motion from said controlling device to said angularly adjustable device to bring saidangularly adjustable device intothe path of said oscillating part connected to said shield. I

11. In a relayapparatus for the purpose described, a mechanism to be operated, a controlling device, a ratchet Wheel connected to said mechanism to be operated, engaging means for said ratchet wheel, means for oscillating said engaging means, a shield between said engaging means and said ratchet wheel, meansfor normally oscillating said shield with said engaging means, angularly adjust-ble means for at times arresting the oscillation of said shield with said engaging means, a rod located to engage with said angularly adjustable-means, a lever carrying said rod, a link connected to said lever and'to said controlling device, a springsupporting the end of said lever away from said rod and means for raising and lowering said spring. v

12. In a relay apparatus for thepurposes 1 means for said ratchet wheel, means for oscillating said engagingmeans, a shield between said engaging means and said ratchet wheel, means for normally oscillating said shield with said engaging means, angular-1y adjustable means for at times arresting the oscillation of said shield with said cngagingmeans, a rod located to engage with said angularly adjustable means, a lever carrying said rod, a link connected to said lever and to said controlling device, a spring supporting the end of said lever away from said rod, an eccentric supporting said spring, a shaft carrying said eccentric and operative connections between the mech- 5 anism to be operated and said shaft to automatically adjust said shaft.

13. In a relay mechanism in which a ratchet wheel is operated by constantly oscillated engaging means normally held out of engagement with the ratchetwheel by a shield controlled by an escapement device, said shield being connected to normally operate with said engaging means; a controlling device, operative connections between said controlling device and said escapement and means for adjusting the ratio of transmission oi: motion from said controlling device to said escapement.

let. In a relay apparatus for the purposes described, a mechanism to be operated, a

controlling device, a ratchet wheel operatively connected to said mechanism to be operated. said ratchet wheel having reversed sets of teeth, two pawls adapted to engage one with each of said sets of teeth, a stud carrying said pawls, an arm carrying said stud, means for constantly oscillating said arm, a shield located between said pawls and the ratchet wheel, means for normally oscilto lating' said shield with said pawls, means connected to said oscillating means for at times arresting the oscillation of said shield.

In a relay apparatus such as described mechanism to be operated, a controlling device, a ratchet wheel carrying rings oi opposing teeth, two pawls arranged one over each of said sets of teeth of said ratchet wheel, means for oscillating said pawls, a shield located between said pawlsand said ratchet wheel, means for oscillating said shield with said pawls, a shaft'coaxial with said ratchet wheel, an arm rigidly mounted on said shaft and carrying said shield, a dish". mounted on said shaft, a pal-- let arranged in rel tion o said disk to, form an escapement device, operative connections between said controlling device and said pallet.

16. in a relay apparatus such as ded a mechanism to be operated, a. con.-

dcvice, a ratchet wheel carrying 655 pawls, a shield located between said pawls opposing teeth, two pawls arranged and said ratchet wheel, means for oscillating said .shield with said pawls, a shaft coaxial with said 'atchet wheel, an arm rigidly mountcd on said shaft and carrying said shield, a disk mounted on said shaft, :1 pallet arranged in relation to said disk to form an escapement device, an upstanding rod under one side of said pallet, a spring; connected to said pallet to press the same on to said. rod, a lever supporting said rod, a link connected to said'lever and carrying one end of said spring and connected to the controlling device, a spring supporting said lever toward one end, means for adjusting the point of support between the said lever and said rod along the length of said lever substantially as described.

17. In a relay apparatus such as de scribed a mechanism to be operated, a controlling device, a ratchet wheel carrying 5 rings of opposing teeth, two pawls arranged one over each of said sets of teeth of said ratchet wheel, means for oscillating said pawls, a shield located between said pawls and-said ratchet wheel, means for oscillating said shield with said pawls, a shaft co axial with said ratchet wheel, an arm rigidly mounted on said shaft and carrying said shield, means connected to and operated by said controlling device to limit the amount of travel of the shield with the pawls and a permanently adjustable shield mounted to rotate withsaid ratchet wheel substantially as described and for the purpose set forth.

18. In a relay apparatus 'suchas described a mechanism to be operated, a controlling device, a ratchet wheel carrying rings of opposing teeth, two pawls arranged one over each of said sets of teeth of said ratchet wheel, means for oscillating said pawls, a shield located between said pawls and said. ratchet wheel, means for oscillating said shield with said pawls, a shaft coaxial with said ratchet wheel, an arm rig-l idly mounted on said shaft andcarrying said shield, means connected to and operated by said controlling device to limit the amount of travel of the shield with the pawls and a permanently adjust-able shield ot a length somewhat'less than the half of the totaltravel of the pawlsin combination witha" furtherpermanently adjustable shield of length greater'than half the total travel of the pawls substantially as and for the'purposc described.

19. In a relay apparatus such as described a mechanism to be operated, a con; trolling device, a "ratchetwheel carrying rings of opposing teeth, two pawls arranged one over each of said sets of teeth of said ratchet wheelfmean s for oscillating said" pawls, a shield located between said pawls and said ratchet wheel, means for oscillating said shield with said pa'wls, a shaft 00- 7 mission of movement from the controlling axial with said ratchet wheel, an arm rigidly mounted on said shaft and carrying said shield, means connected to and operated by said controlling device to limit the amount of tnavel of the shield with the pawls, and means for varying the trans- Witnesses:

of the shield according to fhe position of the mechanism to be operated; 10

In testimony whereof, I afiix my signature, 1n presence of two witnesses.

HERBERT BULLOCK.

HUBERT PUMPHREY,

device to the means for limiting the travel LUCY RANEY. 

